I realize this sounds counterproductive since we don’t want the rear device muted at all, but because of the way the driver settings work, we need this enabled. Under “Playback Device”, enable “Mute the rear output device, when a front headphone plugged in”. The solution: In the Realtek HD Audio Manager (found in Control Panel > Hardware and Sound, or by typing “Realtek” into the Windows search bar), select the gear in the bottom right corner. The specs: Windows 8.1 64-bit, Realtek HD Audio Manager version 6., Gigabyte Z97MX-GAMING 5 mATX motherboard
I wanted to play all desktop sound from both jacks at the same time. Alternately, the computer was treating the front and rear jacks as two separate audio streams rather than one simultaneous stream.
The problem: My computer was muting the rear 3.5mm jack (speakers) when the front 3.5mm jack (headphones) were plugged in.
